The present invention relates to a method and apparatus for determining the location of a sound source. The present invention is particularly suitable for determining the location of a leak in an underground pressurized pipe.
There are many applications where determination of the location of a sound source is required. One such application is the determination of the location of fluid leaks in underground pressurized pipes by use of the sound produced by the leak. Detection of the exact location of fluid leaks in underground pipes is desirable to avoid unnecessary, costly, and time-consuming excavations to find the leak location.
One prior art system for locating underground fluid pipe leaks is disclosed in U.S. Pat. No. 4,083,229, issued Apr. 11, 1978 to A.R. Anway. In the '229 patent, a fluid leak is located by converting the sound intercepted at two points along the pipe into electrical signals using two transducers. The extent of correlation between the two electrical signals is varied by variably time delaying one electrical signal relative to the other electrical signal. The time delay at which the amplitudes of the two electrical signals match-up is used to determine the leak location utilizing the fact that this time delay is indicative of the location of the leak relative to the two transducers.
Unfortunately, since the system disclosed in the '229 patent computes the time delay based upon matching-up signal amplitudes, any frequency dependent amplitude attenuation of the leak sound contributes to inaccuracy in the leak location determination. Since higher frequencies are attenuated more than lower frequencies, the shape of the leak sound waveforms changes as the sound travels. Thus, determining distance information by attempting to match-up a non-delayed waveform and a delayed waveform results in inherent inaccuracies.
Thus, there is a need for a method and apparatus which determines the location of a sound source, such as a pressurized pipe leak, independently of the amplitudes of the generated sound.